ORIGINAL: Big Ray

I have a 99 Deville wit a 4.6 Northstar motor.Heads went bad so I went ahead replace the whole motor. I put a4.6Northstar motor from a 95 sts. Replaced thermostate, water pump, fans work,temperature sensor (thought the cluster might havewent bad). I also put my intake off of my original motor and put it on the 95 sts motor because theintake off of the 95 sts was bigger than mine.When idling, the temperature stays at 190 but when I take off down road it stays at 190. But when i get on highway and reach bout 50 or 60 temperature goes upto 239 but it takes a while,no higher than 239, then it goes back down to 210 then it works its way back up to 239but not quickly only if i go that fast. In the book its says something bout a bleeding off the air pockets in the motor, but doesn't show where they are at. Does any body know where they are at??? Will thats what i think whats wrongit right now. Anybody got any suggestions ???????????????????? Thanks